An adhesive formed with a thermosetting resin or a thermoplastic resin has been used to adhere a semiconductor chip to a substrate.
In FIG. 7, numeral 101 denotes an electronic device containing a semiconductor chip 111 attached to a substrate 113 with an adhesive 112. A bump terminal 121 of the semiconductor chip 111 is in contact with a terminal 122 formed with a part of a wiring pattern on the substrate 113. Under the conditions, an inner circuit of the semiconductor chip 111 is electrically connected to the wiring pattern on the substrate 113 through the terminals 121 and 122. A resin constituting the adhesive 112 has been hardened, and the semiconductor chip 111 and the substrate 113 are mechanically connected to each other with the adhesive 112.
However, because the thermal expansion coefficient of the resin used in the adhesive is generally larger than the thermal expansion coefficient of the semiconductor chip 111, when the electric device 101 shown in FIG. 7 is allowed to stand under high temperature and high humidity conditions, the semiconductor chip 111 is released from the adhesive 112 with a stress occurring at an interface between the adhesive 112 and the semiconductor chip 111 due to the difference in thermal expansion coefficient.
In order to solve the problem, such methods have been employed that an inorganic filler is dispersed in the adhesive 112 to lower the thermal expansion coefficient and the water absorption property of the adhesive 112, and a rubber component is added to the adhesive 112 to lower the elasticity of the adhesive 112 in a hardened state.
However, there are some cases where the adhesive 112 having the inorganic filler or the rubber component dispersed therein causes cracks inside the adhesive 112 due to sudden change in temperature. Particularly, in the case where the filler is added, the rigidity of the adhesive 112 having been hardened is low, and thus cracks is further liable to occur inside the adhesive 112.
In the case where the rubber component is excessively dispersed in the adhesive 112, the thermal expansion coefficient is increased, and as a result, the reliability of the resulting electronic part is lowered. In any case, it is difficult to obtain an electronic part of high reliability by using the conventional adhesive.